Dock levelers are widely used to facilitate the loading and unloading of vehicles at a loading dock. The dock leveler forms a bridge between the building, such as a warehouse or distribution facility, and the back end of the vehicle being loaded or unloaded. A gap typically exists between the building exterior wall and the rear end of the vehicle by virtue of the fact that the vehicle engages against bumpers on the exterior wall. The bumpers are disposed on the wall to protect both the vehicle and the wall against the damage that would result from the vehicle directly engaging the wall. A set of bumpers B, disposed on either side of a dock leveler D, are shown in the prior art FIG. 1. To bridge the gap thus formed, a dock leveler typically employs a deck member, labeled M in FIG. 1, that is hingedly connected about its rear end at H to a support structure disposed within a pit P. Hingedly connected to the front end of the deck D is a lip L which is movable between a downwardly hanging, stored or "pendant" position and the extended position shown in FIG. 1. In the extended position, the lip would be placed in the rear of the vehicle being loaded or unloaded to bridge the gap from the vehicle into the building, and to facilitate loading and unloading. The hinged connection H of the deck to the supporting structure allows the entire leveler to move up and down with the vehicle as it is loaded and unloaded. As a vehicle is unloaded its suspension will tend to raise the floor of the vehicle, and thus the leveler itself. Similarly, as a vehicle is loaded the weight of the cargo will tend to depress the floor of the vehicle against the suspension. Dock levelers are also vertically adjustable in this manner as vehicles are disposed at a wide variety of heights relative to the roadway.
In a typical installation, a pit is formed for receiving the dock leveler. The pit is indicated generally in FIG. 1 by the reference letter P. The pit provides space for the leveler itself, as well as for the actuation mechanism for raising and moving the leveler into its operating positions, and returning it to a stored position. The dock bumpers B are typically disposed on the vertical exterior building wall just laterally of the pit sidewalls. Under certain conditions, this arrangement can be problematic. In FIG. 1, the dock leveler is shown in a so-called below dock position. That is, the deck is disposed at a declined angle with respect to the floor F surrounding the pit P. As can be seen from FIG. 1, the front wall W of the building and the side wall S of the pit P thus form ledges at the front and side edges of the deck, respectively. Certain vehicles to be loaded or unloaded with the leveler may be wider than the width of the dock leveler. In such a situation, the presence of the ledges when the deck is in a below dock position may be a significant impediment to unloading the vehicle. For example, if a load were being removed from a vehicle with a fork truck disposed on the leveler in FIG. 1, and if that load had a width such that a portion of it extended beyond the lateral edge of the lip L and if, for example, there were insufficient headroom inside the vehicle preventing the load from being elevated, that cargo could strike the front wall W of the loading dock or the bumper B, leading to damage of the cargo and/or impeding the efficiency of the unloading process. For this reason, facilities that service a large number of wide vehicles (i.e., vehicles wider than the width of standard dock levelers) often employ truck levelers. Truck levelers are lifts that can lift the vehicle to a raised position relative to the loading dock, so that the vehicle can be serviced by a dock leveler without the need for the dock leveler to assume a below dock position as in FIG. 1, thus avoiding interference between the cargo and the dock wall W or bumper B. The problem of the front wall of the building and the side wall of the dock leveler pit forming a barrier to free and easy movement of cargo being loaded and unloaded could also be solved simply by having a dock leveler of a wider width. However, if a standard dock leveler were as wide a the vehicle itself, there would not be dock wall available for the purpose of mounting bumpers. Thus, there would be the risk that the vehicle would back directly into the leveler, damaging both the leveler and the vehicle itself including impeding the functionality of the dock leveler.